# 控制 UFS 带宽

当Alluxio从底层文件系统（UFS）读取数据时，特别是在缓存预热作业或高缓存未命中期间，流量可能会压垮UFS。这可能会影响依赖于同一UFS的其他应用程序。为防止这种情况，Alluxio允许您限制每个worker上的UFS读取带宽。

## 工作原理

UFS读取速率限制器限制了来自单个Alluxio worker的所有UFS读取的每秒最大带宽。虽然峰值带宽可能偶尔会在非常短的突发中超过配置的限制，但*平均*带宽将被限制在指定的速率。

目前，以下UFS连接器支持此功能：

* HDFS
* 亚马逊S3
* 谷歌云存储（GCS）
* 阿里云OSS
* 腾讯云COS

## 配置

要启用UFS读取速率限制器，请在每个worker的`alluxio-site.properties`中设置以下属性。该值以兆字节/秒（MB/s）为单位指定。

```properties
# Limit UFS read bandwidth to 100 MB/s per worker
alluxio.worker.data.ufs.read.rate.limit.mb=100
```

默认情况下，此功能是禁用的（无限制）。设置此属性将启用具有指定带宽上限的限制器。


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